Monolithic multi-emitting laser device

ABSTRACT

A monolithic laser device produces a plurality of spatially displaced emitting cavities in an active layer of a semiconductor body acting as a waveguide for light wave propagation under lasing conditions. Various means are disclosed to deflect and directly couple a portion of the optical wave propagation into one or more different spatially displaced emitting cavities to improve coherence and reduce beam divergence.

BACKGROUND OF THE INVENTION

This invention relates generally in injection lasers and, moreparticularly, to heterostructure injection lasers having multi-emissioncapability.

Higher power outputs are being sought in semiconductor junction lasersto meet requirements necessary for optical fiber transmission, opticaldisk writing and integrated optical components and circuits. To achievehigher output powers from injection lasers, a wide contact stripe regionhas been proposed wherein stripe widths in excess of, for example, 20μm, were employed in conventionally known double heterojunction andsingle heterojunction injection lasers. The width of the stripe wasincreased to spread the current density over a larger region of thelight guiding layer of the device thereby spreading out the developedpower by virtue of the larger emitting area. This also reduced thepotential of structural damage and degradation of the laser device dueto higher current and power densities established where narrower stripegeometries are employed.

Injection lasers have been known to have a stripe width of approximately75 μm, achieving pulsed output powers of approximately 650 mW.

A disadvantage of these wide stripe lasers has been that transverse modeoperation along the p-n junction plane is not stable. On one hand thesebroad stripe lasers operate in one or more higher order transverse modesexhibiting a broad divergence in the far field radiation pattern, whichpattern may fluctuate with time or with driving current. On the otherhand, multiple filaments may be simultaneously established in the pumpedregions of the light guiding active layer resulting in uncontrolledoptical interference fringes in the laser beam.

Greater power outputs have been realized where more than one contactstripe may be employed on the same laser device and if their stripeseparation is small enough, optical coupling can be achieved due totransverse optical wave overlapping. This is disclosed in U.S. Pat. No.3,701,044 and in Applied Physics Letters, Volume 17, Number 9, pages371-373. With such overlapping, the two established lasers, uponpumping, operate in a phase-locked state. However, as indicated in thesedisclosures, several transverse modes were present so that stable beamoutput was not achieved.

It has already been known that with very narrow stripe geometry, such as2 μm wide, lowest order or fundamental transverse mode can be achievedat least at current pumping levels near threshold. See Japanese Journalof Applied Physics, Volume 16, Number 4, April, 1977, pages 601-607.While such narrower stripe geometry may be used in a multistripeconfiguration, higher order transverse modes may appear at highercurrent levels and a variable range of beam divergence occurs in the farfield pattern over a wide range of pumping currents.

OBJECT AND SUMMARY OF THE INVENTION

It is the general object of this invention to improve the power outputlevel of semiconductor junction laser devices.

It is a further object of this invention to provide a monolithic laserdevice that has a plurality of emitting regions which provide a narrowbeam divergence over a wide range of pumping currents.

In accordance with the present invention, means are provided to deflectand couple a portion of optical waves established in the active layer ina monolithic laser device into other spatially displaced regions of theactive layer. Such means provides for a portion of the optical wavesestablished in any one emitting region or cavity of the active layer tobe deflected and coupled into one or more adjacent or spatiallyestablished emitting cavities of the active layer. This strong directdeflective coupling of light into other regions or into establishedemitting cavities in the active layer of the laser device provides for(1) better coherence resulting in lower beam divergence in the far fieldoptical interference fringe pattern over a wide range of pumpingcurrents and (2) more uniform simultaneous attainance of filamentestablishment among the several emitters for given current threshold.

By direct light deflective coupling, it is meant that some portion ofthe light wave is directly split off, stripped, redirected, steered ordeflected from one emitting region of the active layer to an adjacentemitting region.

In all embodiments to be hereinafter described, the deflection meansemployed provides a refractive index change in the laser device, theeffect of which is to provide direct light deflective coupling as justdefined.

Direct light deflective coupling of the emitting cavities can beaccomplished by interconnecting current confining geometry, or byinterconnecting impurity profile, or by multichannel geometry in thesubstrate of the device, or by a deflection grating or by currentconfining geometry positioned at an angle relative the cleaved ends ofthe device.

Other objects and attainments together with a fuller understanding ofthe invention will become apparent and appreciated by referring to thefollowing description and claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective schematic diagram of a monolithic injectionlaser having multi-emitter capability with current confining means toprovide direct light deflection according to the invention.

FIG. 1a is a perspective schematic diagram of a monolithic injectionlaser having multi-emitter capability with an impurity profile toprovide direct light deflection according to the invention.

FIG. 2 is a perspective schematic diagram of a multi-channeled substrateinjection laser having multi-emitter capability and light deflectionmeans according to the invention.

FIG. .[.2.]. .Iadd.3 .Iaddend.is a partial perspective view of thedetail of the multi-channeled substrate of the laser shown in FIG. 2.

FIG. 4 is a perspective schematic diagram of a mesa injection laserhaving multi-emitter capability and light deflection means according tothe invention.

FIGS. 5a to 5h are schematic illustrations of different contact stripegeometries that may be employed as means to provide deflective opticalcoupling among multi-emitting cavities of a monolithic injection laserdevice. FIGS. 5e and 5f show, in addition, a deflection grating toaccomplish such coupling.

FIG. 6 illustrates the pulsed output power in milliwatts per facet forthe laser shown in FIG. 1.

FIG. 7 illustrates the far field radiation pattern along the p-njunction plane for the laser shown in FIG. 1.

FIG. 8 illustrates the half power beam divergence angle along the p-njunction plane for several types of multi-emitter injection lasers,including the injection laser shown in FIG. 1, as a function of theratio of driving current over threshold current.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The laser devices to be now described are of the double heterostructuretype. However, the means of deflective light coupling disclosed may beincluded in other laser devices, such as, the distributed feedback type,the buried heterostructure type, the single heterostructure type, thehomojunction type, the large optical cavity type, the twin guide type,the transverse junction stripe type or others well known in the art.

Referring to FIG. 1, there is schematically shown in monolithic laserdevice 10 in accordance with one illustrative embodiment of thisinvention. The fabrication of this device 10, as well as other laserstructures hereinafter described, may be fabricated by liquid phaseepitaxy, molecular beam epitaxy or metalorganic processes, whichtechniques are known in the art. Deposited on substrate 12 are layers14, 16, 18 and 20 may comprise, respectively, n-GaAs; n-Ga_(1-z) Al_(z)As; p-Ga_(1-y) Al_(y) As, p-Ga_(1-x) Al_(x) As and n-GaAs, where x and zare greater than y and x and z may be equal. For example, layers 14 and18 may be, respectively, n-Ga₀.65 Al₀.35 As and p-Ga₀.65 Al₀.35 As andlayer 16 may be p-Ga₀.9 Al₀.1 As, making this the active layer with thehighest index of refraction and the lowest bandgap to provide awaveguide for light wave propagation under lasing conditions along theplane of the p-n heterojunction 22. Layers 14, 18, 20 may beapproximately 2 μm thick while active layer 16 may be 0.1 μm thick.

As well recognized in the art, the conductivity type of these layers maybe reversed, which is also true for later described embodiments.

Fabrication of the device 10 is completed by depositing a siliconnitride layer 24 on layer 20. The desired contact stripe geometry isprovided first by forming the geometry through a photolithographic maskby means of plasma etching. This is followed by zinc diffusion throughn-type layer 24 into layer 18, as illustrated at 28 in FIG. 1. Thisdiffusion helps confine the current during pumping.

Conductive layer 26 is then deposited on the selectively etched layer 24to provide a metallization for electrode connection and current pumping.Layer 26 may be gold and chromium. Also the bottom surface of substrate12 metallized to provide a contact for the other electrode connection.This deposited conductive layer 30 may be a gold-tin alloy.

After contact deposition, the ends of device 10 are cleaved to a desiredlength, such as 375 μm.

The current confining channel geometry shown in FIG. 1 comprises tenparallel contact stripes 32. The number of stripes 32 is significantfrom the point of desired power output. Increase in the number ofstripes 32 will proportionally increase the optical power output. Alsothe higher the number of emitting cavities 33, the higher the obtainablepeak power output and the lower the divergence angle of the resultantbeam in the far field.

Upon current pumping of device 10, emitting cavities 33 are produced inactive layer 16 below each contact stripe 32.

Stripe separation 36 from stripe center to center may typically be from2 μm to 25 μm and stripe width 34 may be from 1 μm to 6 μm. Fabricationof the device of FIG. 1 has been done with stripe widths 34 of 3 μm andstripe separations 36 of 10 μm.

If the stripes 32 are closely spaced, that is approximately 8 μm orless, optical coupling will occur because the lateral extent of eachfundamental transverse mode in the emitting cavities 33 under eachcontact stripe 32 will overlap to couple a portion of the light wavegenerated under one stripe 32 into an adjacent contact stripe 32. As aresult, phase locking of the operating modes of all generated lightwaves in the active layer may occur.

However, coherence can be enhanced, reducing beam divergence and providea higher power peak output beam by employing with the monolithic laserdevice 10, means to directly deflect and couple a portion of the opticalwave developed in each of the lasing cavities produced in layer 16 intoone or more adjacent cavities.

Such deflection means may take several forms, one of which is shown inFIG. 1. Each of the contact stripes 32 are directly coupled byinterconnecting contact stripes 38. Interconnecting stripes 38 areprovided in layer 24 during photolithographic and etching processescarried out for contact stripes 32.

The interconnecting stripes 38 may be curved as shown in FIG. 1 or maybe lateral and straight. However, there are many other geometricalconfigurations, as will be explained later in connection with FIGS. 5athrough 5d, that would provide suitable direct light deflectivecoupling.

The curved interconnecting contact stripes 38 may have, for example, aradius of curvature of 1 millimeter from one parallel contact stripe toan adjacent parallel contact stripe.

The curved interconnecting stripes 38 between adjacent stripes 32provide very strong optical coupling between the emitting cavities 33formed in active layer 16. The coupling is strong because portions ofthe optical wave in one particular cavity will split off and bedeflected into different spatially displaced emitter cavities. Such waveportions may be deflected to an adjacent parallel cavity 33 or deflectedinto one or more additional spatially displaced cavities 33. This mannerof deflection of optical wave portions of established optical waves incavities 33 is also true for all other embodiments to be describedhereinafter.

It is noted that contact stripes 32 need not necessarily be positionedclose together to obtain fundamental mode overlapping to provide thebenefits obtained by interconnecting contact stripes 38. Theinterconnecting stripes 38 provide deflective coupling of light toprovide the improved structure without the need of close stripegeometry, such as, 8 μm or less. It is, however, beneficial to havenarrower stripe widths 34 between 2 μm to 4 μm to stabilize fundamentalmode operation.

Typical pumping operation of the laser device 10 may be at 300° K. withcurrent pulses having a pulse width at 800 nanoseconds and a frequencyat 10 KHz. Current thresholds, I_(th), for the cavities 33 may rangebetween 350 and 450 milliamps with threshold attained for all cavities33 with 5% of initial threshold current for the first lasing emittingcavity.

Alternatively, rather current pumping, the laser device may operate witha greater duty cycle or continuous wave while employing a heat sink orthermo-electric cooler.

In summary, the multiple stripe layer device 10 provides currentconfinement defined by the contact stripes 32 and 38 for producing aplurality of light beams 40 in the near field and producing far fieldoptical interference fringe pattern having improved high power and lowbeam divergence. With 10 cavities, it has been found that the poweroutput is also approximately 10 times the power output of a singleemitter cavity. The output power of approximately 1 watt at 65%differential quantum efficiency with far field divergence being within afew degrees over a wide range of pumping currents.

In FIG. 6, the power per facet versus pumping current characteristicsare shown for the laser device 10 of FIG. 1. As shown, thresholdcurrent, I_(th), is approximately 400 milliamps. The curve 42 is linear,exhibiting no current kinks, that is, abrupt changes in power outputunpon uniform increase of pumping current.

In FIG. 7, the angular far field, optical interference fringe pattern 44is shown for the output of the laser device 10 of FIG. 1. This patternis generated by rotating an apertured light pipe in an arc parallel toand centered upon the p-n heterojunction 22. The operating currentemployed during the generation of pattern 44 was 420 milliamps, about 5%above threshold current. Of interest, is the fact that there are aplurality of peaks 46. The number of peaks 46 equals the number ofemitting cavities 33 which indicates the phased locked operation of allof cavities 33.

Also, there are two major diffraction intensity lobes 47 and 48separated by an angle of approximately 5.6°. These lobes are atapproximately -2° and +4° and are different diffracted orders arisingdue to the periodic nature of the established emitter cavities 33. Aminimum intensity point is observed at 0°. The emission of the largestlobe 48 is believed due to an inherent phase delay between adjacentcavities 33.

In FIG. 8 shows a comparison of the full half-power width, divergenceangle for three different types of multi-emission laser devices as afunction of pumping current. Curve 50 represents laser device 10 shownin FIG. 1 having interconnecting contact stripes 38. Curve 52 representsa laser structure similar to that shown in FIG. 1 except that there areno interconnecting contact stripes 38. The laser device for curve 52 hasthe same parallel stripe geometry as the device 10 of FIG. 1 wherestripe width 34 is 3 μm and stripe separation 36 is 10 μm. Thus, anywave coupling and resulting phase locked operation depends solely ontransverse mode wave overlapping and not on actual wave deflection andcoupling accomplished in laser device 10.

Curve 54 also represents a laser structure similar to that shown in FIG.1 but, like the laser device represented by curve 52, there are nointerconnecting contact stripe geometry. The stripe geometry comprises aplurality of parallel contact stripes similar to contact stripes 32 butwith a stripe width 34 of 3.5 μm and a stripe separation 36 of 8 μm.Here, overlapping of the transverse mode wave is much more pronouncedbecause of smaller stripe separation as compared to the laser of curve52.

In FIG. 8, the relative pumping current is represented by the ratio ofactual pumping current, I, over threshold current, I_(th).

The half power width, divergence angle is measured in the far field andis the angle in degrees measured from the cleaved facet of the laserdevice that subtends the half width output of the far field pattern ofthe type shown in FIG. 7. Of interest is the lower beam divergence ofapproximately 1.9° for laser device 10 at threshold current andmaintaining a relatively low divergence angle (approximately 2° to lessthan 5°) over a wide range of pumping currents, i.e., up to about 4.5times threshold current, I_(th). On the other hand, the range ofdivergence angle for the laser devices represented by curves 52 and 54were generally higher (except for curve 54 near threshold) and vary muchmore significantly over a wide range of pumping currents.

Also significant from FIG. 8 is the fact that, the smaller the opticalcoupling between emitting cavities, the less coherence and, therefore,the wider the beam divergence in the far field.

The establishment of emitting regions or cavities in the active layer ofthe laser device may be formed using other fabrication techniques. Theycan be formed by diffusion, ion implantation, chemical etching,preferential crystal growth, sputtering and ion beam milling.

In FIG. 1a, the laser device 51 has the same substrate and fabricatedlayers as laser device 10 of FIG. 1, except that there is no siliconnitride layer 24 Contact layer 26 uniformly covers n-type layer 20. Inorder to provide waveguiding and create optical cavities 33 in theactive layer 16, an impurity profile 53, such as a diffusion (zinc, forexample) or ion implantation, may be extended through layer 18 to activelayer 16. Profile 53 creates a refractive index change in the plane oflayers 16 and 18. Profile 53 as illustrated at the facet 55 of laserdevice 51 extends throughout the device. The geometry of the profile isillustrated by dotted lines 57 on the surface of layer 26. Geometry 57is the same as the geometry for the contact stripes 32, 38 shown inFIG. 1. The interconnection of geometry 57 at 59 illustrates theinterconnecting impurity profile within laser device 51 to provide fordirect light deflective coupling among the established emitting cavities33.

The impurity profile 53 need only extend downwardly into laser device 51to sufficiently permit the light wave established in emitting cavities33 to overlap into and interact with the profile. The profile provides achange in refractive index (both real and imaginery) which stimulatesand guides the light wave according to geometry 57. Interconnectingprofiles at 59 provide a steering mechanism for portions of thepropagating light wave to be deflected and coupled into one or moreadjacent emitting cavities 33.

Referring to FIG. 2, laser device 60 comprises substrate 62 andsequentially deposited layers 64, 66, 68, 70 and 72. These layers may,respectively, comprise n-GaAs; n-Ga₀.65 Al₀.35 As; p-Ga₀.95 Al₀.05 As;p-Ga₀.65 Al₀.35 As; p-GaAs and layer of metalization of a gold-chromiumalloy. A bottom metallic contact 74 may comprise a gold-tin alloy.

A plurality of parallel channels 76 are ion milled or etched intosubstrate 62 prior to growth or deposition of layers 62 through 72.Channel 76 provide mesas 78 therebetween. As best shown in FIG. 3, at apoint along the length of the channels 76, there is provided a series ofinterconnecting channels 80 between adjacent channels 76. Theseinterconnecting channels may be curved, as in the case ofinterconnecting stripes 38 of FIG. 1, or may be transversely disposedrelative to channels 76 as illustrated in FIG. 3. What is important isthat the channels 76 be interconnected in a manner to split off, deflectand guide a portion of developed optical wave from one emitter cavity 82to one or more other adjacent cavities 82.

In laser device 60, T, the thickness of the active layer 66, maytypically be 200A to 0.4 μm or greater; S, the thickness of layer 64above mesas 78, may be 0.2 μm; H, the depth of channels 76, may be 1 μm;D, the periodic width of a channel-mesa combination, may beapproximately 10 μm and W, the width of the channel basin, should beslightly less than D, such as, 8 μm or less.

Upon current pumping, the portions of the active layer 66 above thechannels 76 will provide a waveguide for light wave propagation underlasing conditions and, thus, the establishment of emitter cavities 82.The channels 76 and mesas 78 provide in effect a transverse refractiveindex profile along the plane of the p-n junction 22. The regions abovemesas 78 provide areas in layer 64 of less thickness compared to areasin layer 64 above channels 76. Light waves propagating in emittercavities 82 are stabilized in the fundamental transverse mode in theareas above mesas 78 at the adjacent sides of the established cavities82. Higher order modes do not oscillate because they are absorbed intothese adjacent areas and the propagating wave is induced to stay withinthe confines of the cavity 82.

The same induced losses and light guiding is also obtained throughinterconnecting channels 80 so that portions of optical wave developedin any particular cavity 82 is split off and deflected into one or moreadjacent cavities 82 bringing about phased locked operation and strongercoherence.

The laser device 90, shown in FIG. 4, is similar in semiconductormaterial and current channeling as shown in FIG. 1 except there are onlyfour emitting cavities 91 rather than ten and the device is fabricatedto provide spacing 102 between adjacent cavities. The fabrication oflaser device 90 is as follows. Layers 92, 96, 98 and 100 aresequentially deposited using conventional techniques as previouslyindicated. No isolating or contact layers need be formed on layer 100.Using conventional photolithographic techniques, a mask is prepared onlayer 100, exposed and thereafter controlled etching provides spacings102. The depth 104 of spacings 102 is controlled to be establishedwithin layer 94 adjacent to active layer 96. The resulting structureappears as a plurality of parallel mesa structures 101 coupled byinterconnecting mesa structures 103.

Appropriate contacts can be provided on layer 100 and on the bottom ofsubstrate 92. The resulting structure, upon current pumping, willoperate in the same manner as laser device 10. Spacings 102 providebetter current confinement properties than possibly obtainable inconnection with laser device 10 of FIG. 1.

The spacing 102 between provides for a medium, air, which has a lowindex of refraction than active layer 96. This spacing may also befilled with a semiconductor material deposited during a second sequenceof growth. The material chosen should have a lower index of refractionthan active layer 96.

It is of interest to mention at this point that the laser devices 10 and90 provide current confining channels to establish the emitting cavitieswhile laser device 51 provides a impurity profile to establish emittingcavities and laser device 60 provides a material thickness change toestablish the emitting cavities. In any case, what is effectively beingaccomplished is a change in the refractive index (both the real andimaginary parts) at regions where the emitting cavities are created. Thestripe geometry of laser device 10 can be combined with the identicalchannel geometry of laser device 60. Also, other types of currentconfining channels, such as, buried heterostructure geometry, buriedstripe geometry, substrate stripe and implanted stripe, may be employedin the substrate of these laser devices to provide direct deflectivecoupling. Such buried stripe fabrication is disclosed in U.S. Pat. No.4,099,999 issued July 11, 1978 and assigned to the assignee herein.

There are many ways of employing interconnecting current confiningchannel geometry as a means to deflect and couple portions of split offoptical waves among the various emitting cavities. In FIGS. 5a through5d, various examples of interconnecting geometry is illustrated. IN FIG.5a, the parallel contact stripes 106 are interconnected by means ofcriss-cross interconnecting stripes 108. In this embodiment, deflectionmay occur in either direction of light wave propagation. In FIG. 5b,parallel contact stripes 110 are provided with curved sections 112ending in a single stripe section 114. These sections 112 and 114 form ay-shaped interconnecting means. Curved sections 112 aid in establishingfundamental mode operation and provide means to split off and deflectportions of the developed optical wave into one or more adjacentcavities.

In FIG. 5c, the parallel contact stripes 116 are interconnected in anoffset manner along the length of the device by transversely disposedinterconnecting stripes 118. Each interconnecting stripe 118 isdisplaced relative to an adjacent interconnecting stripe 118 along thelength of the laser device.

In FIG. 5d, the parallel contact stripes 120 are interconnected by asingle transverse contact stripe 122. Stripe 122 has a larger width thanindividual stripes 120 and may be disposed laterally at an angle acrossstripes 120 as well as perpendicular thereto as shown in the Figure.

The laser device 130 shown in FIGS. 5e and 5f illustrates the use of agrating as a means of splitting off and deflecting a portion of theestablished light wave in the active layer into other regions of theactive layer. Rather than establishing emitting cavities in the activelayer, the entire active layer is pumped. However, parallel contactstripes could be provided on the surface of the device 130 to establishseparate emitting cavities and the grating used to deflect and couplelight waves from one or more cavities into one or more other adjacentcavities.

Structurally, laser device 130 may be similar to laser device 10 in FIG.1, i.e., layers 132, 134, 136, 138 140, and 142 of device 130 arecomparable to layers 12, 14, 16, 18, 20 and 26 of device 10. Contactlayer 142 covers the entire surface of device 130. A grating pattern 146is provided, for example in layer 134, adjacent to active layer 136, todeflect and couple portions of an established optical light wave in oneregion of the active layer into other regions of the active layer 136 ina manner depicted by arrow 147.

The grating pattern 146 may be disposed at 45° relative to the cleavedends 148 of the device 130. However, other angles may be used as well.The grating period Λ is given by Λ=pλo sinθ/n_(eff) where λ_(o) is thefree space laser wavelength, θ is the angle of the grating relative tothe lasing beam path, n_(eff) is the effective refractive index seen bythe laser light and p is an integer. If the grating is at 45° to thebeam direction and if the laser operates at 8000A with n_(eff) =3.6, agrating period of integer multiples of 1571A may be used.

In FIG. 5g, the plurality contact stripes 150 are positioned at anoffset angle φ relative to the longitudinal length of the laser device.The angularity of the stripes 150 is exaggerated for purposes ofexplanation. In practice, this angle may be 1° with the contact stripeshaving a 2 μm width and an 8 μm separation from stripe center to center.The length of the device may be approximately 250 μm.

A portion of the optical wave propagating along an emitting cavity ofthe active layer will be deflected, upon light beam reflection at eithercleaved facet 152 of the device, into an adjacent emitting cavity. Thisis because the angle of incidence of the optical wave is not normal tothe cleaved facets so that a portion of the optical wave will bereflected from the mirror surfaces of facets 152 into an adjacent cavityas depicted by arrow 154.

In FIG. 5h, the contact stripes 156 are not parallel but positionedangularly relative to each other in a manner that a portion of the lightwave incident to the cleaved facet 158 is reflected and coupled into anadjoining emitting cavity. This deflective coupling is accomplished byinterconnected stripe geometry 160 at the ends of stripes 156. Arrow 162represents portions of light deflected from one established emittingcavity to an adjoining cavity.

In this embodiment as well as other embodiments of FIGS. 5, rather thanemploying current confining channels, such as, contact stripes 158, adiffused or implanted material composition change providing a refractiveindex profile corresponding to such channel geometry sufficientlydiffused and implanted into the device to effectively interact with thelight wave will also produce the direct light deflective couplingprovided by these channel geometries.

Although in all the foregoing illustrations, the means to providedeflective coupling have been illustrated in an equally spaced manner,they may be positioned to have variable or unequal spacing to providebeam focusing or to provide side lobe suppression thereby enhancing thefundamental lobe (such as, lobe 48 at +4° in FIG. 7) in the far field.

Also, the current confining channels need not be defined by oxide orcontact stripes as shown in the Figures. Any other well known currentconfining technique such as ion implantation, diffusion, substratestripes, planar stripes, mesa stripe, internal strip transverse junctionstripe etc. may be used.

Also, as shown in the Figures the deflective means for coupling lightfrom one region of the active layer to another has been shown to bepresent near or within the active layer. However, the deflective meanscould be removed from close proximity to the active layer by couplinglight from the active layer into a transparent waveguide layer. A numberof methods for coupling light into transparent waveguide layers such astwin guide lasers, taper coupled lasers and others are well known in theart. Once in the transparent waveguide, the light deflective means suchas is provided by a refractive index change could be used to deflect thelight back into other spatially displaced regions of the active layerthus allowing for strong optical coupling of spatially separated regionsof the active layer.

Although all the foregoing embodiments have been described in connectionwith semiconductor materials of GaAs and GaAlAs, other light emittingmaterials may be employed, such as InGa, AsP, GaAlP, GaAlSb, and PbSnTe.

While the invention has been described in conjunction with specificembodiments, it is evident that many alternatives, modifications andvariations will be apparent to those skilled in the art in light of theforegoing description. Accordingly, it is intended to embrace all suchalternatives, modifications, and variations as fall within the spiritand scope of the appended claims.

We claim:
 1. In a monolithic laser device wherein one or more layers of semiconductor material are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave propagation and generation under lasing conditions, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend.to produce a plurality of adjacent .Iadd., linear .Iaddend.light propagating and emitting portions therein, light guiding regions in said device .Iadd.intermediate of the ends of and .Iaddend.nonlinear relative to said emitting portions whereby .[.said.]. .Iadd.the .Iaddend.light waves produced in one portion of said active .[.layer.]. .Iadd.means .Iaddend.are deflected and coupled into one or more adjacent emitting portions of said active .[.layer.]. .Iadd.means .Iaddend., said regions provided by a refractive index change with which .[.said.]. .Iadd.the .Iaddend.light wave interacts while .[.said light wave is.]. within said regions and wherein said refractive index change is provided by the injected charge distribution determined by current confining means.
 2. In a monolithic laser device wherein one or more layers of semiconductor material are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave propagation and generation under lasing conditions, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend., means in .Iadd.and intermediate of the ends of .Iaddend.said device whereby .[.said.]. .Iadd.the .Iaddend.light waves produced in one portion of said active .[.layer.]. .Iadd.means .Iaddend.are deflected into one or more adjacent emitting portions of said active .[.layer.]. .Iadd.means .Iaddend., said deflection means provided by a refractive index change with which .[.said.]. .Iadd.the .Iaddend.light wave interacts while .[.said light wave is.]. within said deflection means and wherein said refractive index change is provided by an impurity profile.
 3. The device of claim 2 wherein said impurity profile defines a plurality of .Iadd.linear .Iaddend.optical cavities, said cavities being coupled to one or more adjacent cavities by an interconnecting cavity formed by said profile.
 4. The device of claim 3 wherein said optical cavities are angularly disposed relative to each other.
 5. The device of claim 3 wherein said optical cavities are parallel.
 6. The device of claim 3 wherein said optical cavities are unequally spaced relative to each other.
 7. The device of claim 3 wherein some of said optical cavities are unequally spaced.
 8. The device of claim 3 wherein all of said optical cavities are equally spaced relative to each other.
 9. In a monolithic laser device wherein one or more layers of semiconductor material are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave propagation and generation under lasing conditions, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend., means in .Iadd.and intermediate of the ends of .Iaddend.said device whereby .[.said.]. .Iadd.the .Iaddend.light waves produced in one portion of said active .[.layer.]. .Iadd.means .Iaddend.are deflected into one or more adjacent emitting portions of said active .[.layer.]. .Iadd.means .Iaddend., said deflection means provided by a refractive index change with which .[.said.]. .Iadd.the .Iaddend.light wave interacts while .[.said light wave is.]. within said deflection means and wherein said deflection means is a plurality of current confining channels, each of said current confining channels being coupled to an adjacent channel by an interconnecting current confining channel.
 10. The device of claim 9 wherein said current confining channels are contact stripes.
 11. The device of claim 9 wherein said current confining channels are angularly disposed relative to each other.
 12. The device of claim 9 wherein said current confining channels are parallel.
 13. The device of claim 9 wherein said current confining channels are unequally spaced relative to each other.
 14. The device of claim 9 wherein some of said current confining channels are unequally spaced.
 15. The device of claim 9 wherein all of said current confining channels are equally spaced relative to each other.
 16. In a monolithic laser device wherein one or more layers of semiconductor material are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave propagation and generation under lasing conditions, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend., means in .Iadd.and intermediate of the ends of .Iaddend.said device whereby .[.said.]. .Iadd.the .Iaddend.light waves produced in one portion of said active .[.layer.]. .Iadd.means .Iaddend.are deflected into one or more adjacent emitting portions of said active .[.layer.]. .Iadd.means .Iaddend., said deflection means provided by a refractive index change with which .[.said.]. .Iadd.the .Iaddend.light wave interacts while .[.said light wave is.]. within said deflection means and wherein said refractive index change is provided by a material composition change.
 17. The device of claim 16 wherein the material composition change defines a plurality of .Iadd.linear .Iaddend.optical cavities, said cavities being coupled to one or more adjacent cavities by an interconnecting cavity formed by said material composition change. .[.18. The device of claim 17 wherein said optical cavities are angularly disposed relative to each other..].
 19. The device of claim 17 wherein said optical cavities are parallel.
 20. The device of claim 17 wherein said optical cavities are unequally spaced relative to each other.
 21. The device of claim 17 wherein some of said optical cavities are unequally spaced.
 22. The device of claim 17 wherein all of said optical cavities are equally spaced relative to each other.
 23. In a monolithic laser device wherein one or more layers of semiconductor material are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave propagation and generation under lasing conditions, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend., means in .Iadd.and intermediate of the ends of .Iaddend.said device whereby .[.said.]. .Iadd.the .Iaddend.light waves produced in one portion of said active .[.layer.]. .Iadd.means .Iaddend.are deflected into one or more adjacent emitting portions of said active .[.layer.]. .Iadd.means .Iaddend., said deflection means provided by a refractive index change with which .[.said.]. .Iadd.the .Iaddend.light wave interacts while .[.said light wave is.]. within said deflection means and wherein said refractive index change is provided by a material thickness change. . The device of claim 23 wherein a plurality of interconnecting channels are provided in said substrate to provide said material thickness change.
 5. The device of claim 23 wherein the material thickness change defines a plurality of .Iadd.linear .Iaddend.optical cavities, said cavities being coupled to one or more adjacent cavities by an interconnecting cavity formed by said material thickness change. .[.26. The device of claim 25 wherein said optical cavities are angularly disposed relative to each other..].
 27. The device of claim 25 wherein said optical cavities are parallel.
 28. The device of claim 25 wherein said optical cavities are unequally spaced relative to each other.
 29. The device of claim 25 wherein some of said optical cavities are unequally spaced.
 30. The device of claim 25 wherein all of said optical cavities are equally spaced relative to each other.
 31. In a monolithic laser device wherein one or more layers of semiconductor material are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave propagation and generation under lasing conditions, current confining means for forward biasing selected portions of said active .[.layer.]. .Iadd.means .Iaddend.to produce two or more .Iadd.linear and spatially disposed .Iaddend.lasing and .Iadd.light .Iaddend.emitting cavities in said active .[.layer.]. .Iadd.means .Iaddend., and a light coupling region between said .Iadd.linear light emitting .Iaddend.cavities to deflect a portion of the light wave propagation in one cavity to one or more adjacent emitting cavities.
 32. In a monolithic laser device wherein one or more layers of semiconductor material are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave propagation and generation under lasing conditions, a plurality of current confining means for forward biasing selected portions of said active .[.layer.]. .Iadd.means .Iaddend.to produce a plurality of .Iadd.linear light .Iaddend.emitting cavities therein, and light deflecting means .Iadd.intermediate of the ends of said cavities and .Iaddend.coupling each of said current confining means to one or more adjacent current confining means wherein said current confining means comprises a plurality of parallel contact stripes on the surface thereof, each of said stripes being coupled to an adjacent stripe by an interconnecting stripe means. The device of claim 32 wherein said interconnecting stripe means are curved stripe sections.
 34. The device of claim 32 wherein said interconnecting stripe means are transversely disposed stripe sections. The device of claim 34 wherein said sections are geometrically staggered relative to each other along the length of said device.
 36. The device of claim 32 wherein said interconnecting stripe means are criss-crossing stripe sections.
 37. The device of claim 32 wherein said interconnecting stripe means comprises a single wide contact stripe transversely disposed relative to said parallel .[.contract.]. .Iadd.contact .Iaddend.stripes, said transversely disposed stripe being several times wider than said parallel contact stripes.
 38. The device of claim 37 wherein said transversely disposed stripe is perpendicular to said parallel contact stripes.
 39. The device of claim 32 wherein said interconnecting stripe means comprises a y-shape stripe configuration connecting the ends of a pair of said parallel contact stripes at one end of said device.
 40. The device of claim 32 wherein said contact stripes are disposed at an angle relative to the longitudinal axis of said device.
 1. The device of claim 32 wherein said current confining means comprises a plurality of contact stripes on the surface thereof, said stripes being angularly disposed relative to each other and said interconnecting stripe means connecting the ends of adjacently disposed contact stripes.
 42. In a monolithic laser device wherein one or more layers of semiconductor materials are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave generation and propagation, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend.to produce a light wave in at least one linear light propagating region of said active .[.layer.]. .Iadd.means .Iaddend.and an adjacent light guiding region .Iadd.intermediate of the ends of and .Iaddend.coupled to said one region to deflect and couple a portion of said light wave in said one region into other such regions formed in said active .[.layer.]. .Iadd.means .Iaddend.which are linear and spatially displaced from said one region.
 43. In a monolithic laser device wherein one or more layers of semiconductor materials are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave generation and propagation, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend.to produce a light wave in at least one region of said active .[.layer.]. .Iadd.means .Iaddend.and means to deflect and couple a portion of said light wave in said one region into other regions of said active .[.layer.]. .Iadd.means .Iaddend.spatially displaced from said one region and wherein said first and second mentioned means include means to confine current to selected portions of said active layer to produce multiple .Iadd.linear light .Iaddend.emitting cavities.
 44. In a monolithic laser device wherein laser device wherein one or more layers of semiconductor materials are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.medium .Iaddend.for light wave generation and propagation, means for forward biasing said active .[.layer.]. .Iadd.medium .Iaddend.to produce a light wave in at least one region of said active .[.layer.]. .Iadd.medium .Iaddend.and means to deflect and couple a portion of said light wave in said one region into other regions of said active .[.layer.]. .Iadd.medium .Iaddend.spatially displaced from said one region and wherein said first mentioned means comprises a plurality of current confining channels, said second mentioned means comprises a plurality of interconnecting current confining channels .Iadd.intermediate of the ends of the ends of said regions. .Iaddend.. The device of claim 44 wherein said current confining channels comprises a plurality of spaced stripes, said interconnecting current confining channels comprise a plurality of interconnecting stripes, at least one such interconnecting stripe being disposed between adjacent stripes.
 46. In a monolithic laser device wherein one or more layers of semiconductor materials are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.medium .Iaddend.for light wave generation and propagation.Iadd., .Iaddend.means for forward biasing said active .[.layer.]. .Iadd.medium .Iaddend.to produce a light wave in at least one region of said active .[.layer.]. .Iadd.medium .Iaddend.and means to deflect and couple a portion of said light wave in said one region into other regions of said active .[.layer.]. .Iadd.medium .Iaddend.spatially displaced from said one region and wherein said first mentioned means comprises a plurality of spaced mesa structures including .[.all.]. .Iadd.portions .Iaddend.of said layers .Iadd.and said active medium .Iaddend., said mesa structures separated from each other by a medium of lower refractive index than said active .[.layer.]. .Iadd.medium .Iaddend., and said second mentioned means comprises a plurality of interconnecting mesa structures .Iadd.intermediate of the ends of said mesa structures .Iaddend., at least one such interconnecting mesa structure being disposed between adjacent mesa structures.
 47. In a monolithic laser device wherein one or more layers of semiconductor materials are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.medium .Iaddend.for light wave generation and propagation, means for forward biasing said active .[.layer.]. .Iadd.medium .Iaddend.to produce a light wave in at least one region of said active .[.layer.]. .Iadd.medium .Iaddend.and means to deflect and couple a portion of said light wave in said one region into other regions of said active .[.layer.]. .Iadd.medium .Iaddend.spatially displaced from said one region and wherein said first mentioned means comprises a plurality of spaced channels in the surface of said substrate, said second mentioned means comprises a plurality of interconnecting channels in said substrate .Iadd.intermediate of the ends of the ends of said spaced channels .Iaddend., at least one such interconnecting channel being disposed between adjacent channels.
 48. In a monolithic laser device wherein one or more layers of semiconductor materials are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave generation and propagation, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend.to produce a light wave in at least one region of said active .[.layer.]. .Iadd.means .Iaddend.and means to deflect and couple a portion of said light wave in said one region into other regions of said active .[.layer.]. .Iadd.means .Iaddend.spatially displaced from said one region and wherein said .[.second.]. .Iadd.third .Iaddend.mentioned means is a periodic grating disposed in said layers such that said light wave interacts with said grating being at an angle relative to the direction of light wave propagation.
 49. In a monolithic laser device wherein one or more layers of semiconductor materials are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.medium .Iaddend.for light wave generation and propagation, means for forward biasing said active .[.layer.]. .Iadd.medium .Iaddend.to produce a light wave in at least one region of said active .[.layer.]. .Iadd.medium .Iaddend.and means to deflect and couple a portion of said light wave in said one region into other regions of said active .[.layer.]. .Iadd.medium .Iaddend.spatially displaced from said one region and wherein said first mentioned means comprises a plurality of current confining channels, said second mentioned means characterizes said current confining channels as each being disposed at an angle relative to the longitudinal axis of said device.
 50. The device of claim 49 wherein said current confining channels are parallel. . The device of claim 49 wherein said current confining channels are angularly disposed relative to each other and coupled to an adjacent current confining channel by interconnecting channel means.
 52. The device of claims 49, 50 or 51 wherein said current confining channels are contact stripes.
 53. In a monolithic laser device wherein one or more layers of semiconductor materials are fabricated on a substrate, one of said layers forming .[.an.]. active .[.layer.]. .Iadd.means .Iaddend.for light wave generation and propagation, means for forward biasing said active .[.layer.]. .Iadd.means .Iaddend.to produce a light wave in at least one region of said active .[.layer.]. .Iadd.means .Iaddend.and means to deflect and couple a portion of said light wave in said one region into other regions of said active .[.layer.]. .Iadd.means .Iaddend.spatially displaced from said one region and wherein said regions are impurity in said device, said impurity profile defining a plurality of .Iadd.linear .Iaddend.optical cavities, said .Iadd.linear optical .Iaddend.cavities being coupled to one or more adjacent cavities by an interconnecting cavity formed by said profile .Iadd.and intermediate of the ends of said cavities .Iaddend.. .Iadd.54. The device of claim 31 wherein said linear cavities are coupled by said light coupling regions intermediate of the ends of said linear cavities. .Iaddend. .Iadd.55. The device of claim 31 wherein said linear cavities are angularly disposed relative to adjacent, linear cavities and are coupled to said adjacent, linear cavities by said light coupling regions at the ends of said cavities. .Iaddend. .Iadd.56. The device of claim 43 wherein said linear emitting cavities are coupled by said deflection means intermediate of the ends of said linear emitting cavities. .Iaddend. .Iadd.57. The device of claim 43 wherein said linear emitting cavities are angularly disposed relative to adjacent, linear cavities and are coupled to said adjacent, linear cavities by said deflection means at the ends of said cavities. .Iaddend. 